Since under the effect of heat that is generated either during industrial-scale synthesis or during purification by distillation, organic silicon compounds that contain methacryloxy groups or acryloxy groups are subject to spontaneous polymerization, and selection of polymerization inhibitors for preventing the undesired spontaneous polymerization is a matter of great importance.
Japanese Unexamined Patent Application Publication [hereinafter referred to as Kokai] S62-283983 (equivalent to EP 0247501) discloses a manufacturing method where an aromatic sulfur compound represented by phenothiazine is used as an inhibitor during distillation and synthesis of an organic silane that contains methacryloxy and acryloxy groups. However, during purification by distillation, the phenothiazine is easily mixed with fractions, and since the final product is admixed with phenothiazine, it is subject to severe coloration.
Kokai H5-186478 (equivalent to EP 0520477) discloses inhibition of polymerization of an acryloxysilane and methacryloxy silane by adding to the composition an N,N-dialkylaminomethylene phenol. Kokai H5-230143 discloses a polymerization inhibitor having an active ingredient in the form of an isocyanuric acid hydroxybenzyl ester derivative, e.g., isocyanuric acid tris(3,5-di-tert-butyl-4-hydroxybenzyl)ester. Kokai H7-25907 discloses a polymerization inhibitor having an active ingredient in the form of a 2,6-di-t-butyl-4-hydroxymethylphenol. Although the last-mentioned polymerization inhibitors are relatively resistant to coloration when mixed with the final product, they are still unsuitable for production under conditions of high temperature and strong acidity inherent in an industrial manufacturing process.